Verification of the H2O Linelists with Theoretically Developed Tools

Two basic rules (i.e., the pair identity and the smooth variation rules) resulting from the properties of the energy levels and wave functions of H2O states govern how the spectroscopic parameters vary with the H2O lines within the individually defined groups of lines. With these rules, for those lines involving high j states in the same groups, variations of all their spectroscopic parameters (i.e., the transition frequency, intensity, pressure broadened half-width, pressure-induced shift, and temperature exponent) can be well monitored. Thus, the rules can serve as simple and effective tools to screen the H2O spectroscopic data listed in the HITRAN database and verify the latter's accuracies. By checking violations of the rules occurring among the data within the individual groups, possible errors can be picked up and also possible missing lines in the linelist whose intensities are above the threshold can be identified. We have used these rules to check the accuracies of the spectroscopic parameters and the completeness of the linelists for several important H2O vibrational bands. Based on our results, the accuracy of the line frequencies in HITRAN 2008 is consistent. For the line intensity, we have found that there are a substantial number of lines whose intensity values are questionable. With respect to other parameters, many mistakes have been found. The above claims are consistent with a well known fact that values of these parameters in HITRAN contain larger uncertainties. Furthermore, supplements of the missing line list consisting of line assignments and positions can be developed from the screening results

Verification of H2O lines from the HITRAN database for remote sensing of the water vapour isotopic composition

The quality of the spectroscopic line parameters from the HITRAN Database for remote sensing of the water vapour isotopic composition of the atmosphere is widely discussed. In this research we show that the HITRAN-2008 data for H2O isotopologues in the near infrared spectral range (4000-6400 cm-1) is reasonably good. The HITRAN data was tested with independent calculation (ab initio et al.). For the evaluation we've used two following criteria: a quality of the fitting of atmospheric spectra measured at the Ural Atmospheric Station (UAS, Kourovka) with the high-resolution Fourier-transform infrared spectrometer and an agreement between the retrieved HDO/H2O relative concentration ratios in the atmospheric column and the results of the simulation of the isotopic general circulation model ECHAM5-wiso (validated for Kourovka region). © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

The HITRAN2020 Molecular Spectroscopic Database

The HITRAN database is a compilation of molecular spectroscopic parameters. It was established in the early 1970s and is used by various computer codes to predict and simulate the transmission and emission of light in gaseous media (with an emphasis on terrestrial and planetary atmospheres). The HITRAN compilation is composed of five major components: the line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, experimental infrared absorption cross-sections (for molecules where it is not yet feasible for representation in a line-by-line form), collision-induced absorption data, aerosol indices of refraction, and general tables (including partition sums) that apply globally to the data. This paper describes the contents of the 2020 quadrennial edition of HITRAN. The HITRAN2020 edition takes advantage of recent experimental and theoretical data that were meticulously validated, in particular, against laboratory and atmospheric spectra. The new edition replaces the previous HITRAN edition of 2016 (including its updates during the intervening years). All five components of HITRAN have undergone major updates. In particular, the extent of the updates in the HITRAN2020 edition range from updating a few lines of specific molecules to complete replacements of the lists, and also the introduction of additional isotopologues and new (to HITRAN) molecules: SO, CH3F, GeH4, CS2, CH3I and NF3. Many new vibrational bands were added, extending the spectral coverage and completeness of the line lists. Also, the accuracy of the parameters for major atmospheric absorbers has been increased substantially, often featuring sub-percent uncertainties. Broadening parameters associated with the ambient pressure of water vapor were introduced to HITRAN for the first time and are now available for several molecules. The HITRAN2020 edition continues to take advantage of the relational structure and efficient interface available at www.hitran.org and the HITRAN Application Programming Interface (HAPI). The functionality of both tools has been extended for the new edition

The HITRAN2020 molecular spectroscopic database

The HITRAN database is a compilation of molecular spectroscopic parameters. It was established in the early 1970s and is used by various computer codes to predict and simulate the transmission and emission of light in gaseous media (with an emphasis on terrestrial and planetary atmospheres). The HITRAN compilation is composed of five major components: the line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, experimental infrared absorption cross-sections (for molecules where it is not yet feasible for representation in a line-by-line form), collision-induced absorption data, aerosol indices of refraction, and general tables (including partition sums) that apply globally to the data. This paper describes the contents of the 2020 quadrennial edition of HITRAN. The HITRAN2020 edition takes advantage of recent experimental and theoretical data that were meticulously validated, in particular, against laboratory and atmospheric spectra. The new edition replaces the previous HITRAN edition of 2016 (including its updates during the intervening years). All five components of HITRAN have undergone major updates. In particular, the extent of the updates in the HITRAN2020 edition range from updating a few lines of specific molecules to complete replacements of the lists, and also the introduction of additional isotopologues and new (to HITRAN) molecules: SO, CH3F, GeH4, CS2, CH3I and NF3. Many new vibrational bands were added, extending the spectral coverage and completeness of the line lists. Also, the accuracy of the parameters for major atmospheric absorbers has been increased substantially, often featuring sub-percent uncertainties. Broadening parameters associated with the ambient pressure of water vapor were introduced to HITRAN for the first time and are now available for several molecules. The HITRAN2020 edition continues to take advantage of the relational structure and efficient interface available at www.hitran.org and the HITRAN Application Programming Interface (HAPI). The functionality of both tools has been extended for the new edition

Temperature-dependence parameters for CH3I-O2 and CH3I-air line-broadening coefficients

International audienceTaking advantage of the temperature-invariant semi-empirical model parameters determined previously at room temperature [JQSRT 273, 107839 (2021)], CH3I-O2/air line-broadening coefficients in the interval 200–400 K recommended for HITRAN are calculated for the R,PP, R,PQ and R,PR sub-branches of the ν6 band and a large range of quantum numbers (0 ≤ J ≤ 70, K ≤ 20) generally requested by spectroscopic databases. These theoretical estimates are further used to extract the associated temperature-dependence parameters. As perfectly linear fits in log-log coordinates are obtained with the traditional power law, the deduced temperature-dependence exponents ensure an accurate description of the line-broadening coefficients at any temperature in the considered temperature range and more advanced models such as double-power law are not applicable. Since no not-room temperature measurements are currently available, these data can be extremely useful for terrestrial-atmosphere applications involving methyl iodide. The values computed for the ν6 band can be also used as reasonable estimates for other parallel and perpendicular bands due to the negligible sub-branch dependence and weak vibrational dependence

Line broadening of SO2 and CO2 volcanic activity gases in the Earth’s atmosphere

Calculations of the CO2-broadening coefficients of sulfur oxide lines by the semi-empirical method [Mol. Phys. 102 (2004) 1653] and averaged energy difference method [Atmosph. Ocean. Optics 28 (2015) 403] are presented. In this work, 41 lines are considered, the rotational quantum number J varies from 14 to 51. Calculations of the line widths are carried out for room temperature (296 K), and also for the temperature range typical for the Ears atmosphere. There is good agreement with the literature data. The carbon dioxide lines broadening coefficients induced by nitrogen, nitrogen oxide, carbon monoxide and carbon dioxide at room temperature (T = 296 K) are obtained for a wide range of the rotational quantum number J (up to 100). The temperature exponents are calculated for every line widths. The calculations were performed by a semi-empirical method, based on the semiclassical impact theory of line broadening and modified by introducing additional correction factor whose parameters can be determined by fitting the broadening or shifting coefficients to the experimental data

Temperature-dependence exponents for CH3I-N2 line-broadening coefficients

International audienceTemperature-dependence exponents of the traditional power law relating line-broadening coefficients at experimental and reference temperatures are deduced for CH3I-N2 lines in the ν6 band from theoretical estimates in the temperature interval 200–400 K recommended for HITRAN. Perfectly linear fits in log-log coordinates indicate that this simple law is sufficient and more advanced models such as the double-power law are not applicable. Calculations are performed by a semi-empirical method employing room-temperature-adjusted model parameters which remain valid for other temperatures. Results are provided for all six sub-branches of the considered band and cover a large range of quantum numbers (0 ≤ J ≤ 70, K ≤ 20) requested typically by spectroscopic databases. In the absence of measurements at not-room temperatures, these data can be extremely useful for atmospheric applications involving methyl iodide, in particular for the terrestrial atmosphere. Given the negligible vibrational dependence of nitrogen-broadened CH3I line widths, the values computed for the ν6 fundamental can be safely used for other parallel and perpendicular bands

Room-temperature CH 3 I-N 2 broadening coefficients for the ν 6 fundamental

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Oxygen- and air-broadening coefficients for the CH 3 I ν 6 fundamental at room temperature

International audienceCHI-oxygen line-broadening coefficients at 296 K are calculated for the RR, PR, RP, PP, RQ and PQ sub-branches of the band in a wide range of rotational quantum numbers (, by a semi-classical and a semi-empirical methods. The computed values compare very favourably with the available experimental data and therefore can be safely employed as estimates of broadening coefficients missing in databases for high and . The theoretical data for CHI-O are further combined with the previously calculated room-temperature CHI-N line-broadening coefficients to obtain the air-broadening values required for atmospheric applications. The calculated results demonstrate an excellent consistency with both existing sets of CHI-air measurements. As the vibrational dependence of CHI oxygen-broadening coefficients is shown to be small, similarly to the nitrogen-broadening case, the CHI-O and CHI-air line-broadening coefficients calculated for the fundamental can be used for other perpendicular and parallel bands

Temperature dependence of CH3I self-broadening coefficients in the ν6 fundamental

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